Average chemical composition, determined by 872 chemical analyses of dioritic rocks1 (numbers are mass percents, recalculated volatile-free to total 100%): SiO2 — 58.34 It frequently contains smaller amounts of pyroxene (usually augite but also orthopyroxene), biotite, quartz, olivine, and magnetite. It is quartz diorite. The grey or dark grey diorite is very common to spot in the world. Diorite, being a mix of minerals, varies in its properties, but generally it is hard (its dominant minerals having hardnesses of around 6 on the Mohs scale). Mafic rocks are darker and are composed of magnesium and iron. marble - metamorphic rock that cannot fall into these categories. Diorite: intermediate with a phaneritic texture (crystals are so coarse that individual minerals can be distinguished with the naked eye) Rhyolite: felsic with an aphanitic texture (so fine-grained that their component mineral crystals are not detectable by the unaided eye) Width of sample 9 cm. Subsequently, one may also ask, is granite mafic felsic or intermediate? mafic 96: - Based on your estimate, describe this rock as felsic, intermediate, mafic, or ultramafic. Salt and pepper appearance and the mineralogy is also just right: hornblende with plagioclase, but it is not diorite. One comparatively frequent use of diorite was for inscription, as it is easier to carve in relief than in three-dimensional statuary. Width of sample 8 cm. Heat would destroy them. a “felsic” light color. 139 HOLIC Lab #6-Igneous Rock Samples Red Granite Rhyolite Diorite Gabbro Gray Granite Obsidian Andesite Basalt Rhyolite Tuff Pumice Accessory minerals include apatite, sphene (titanite), ilmenite, zircon, etc. TiO2 — 0.96 Igneous Rocks Chemical composition Felsic Granite Rhyolite Intermediate Diorite from GEOL 118 at University of Michigan Gabbro would have more ferromagnesian minerals than Granite. Mafic magma is less viscous than felsic magma. Diorite in the wider sense (yellow) includes adjacent fields of quartz diorite, quartz monzodiorite, monzodiorite, foid-bearing monzodiorite (foid is a shorter way to say feldspathoid), foid-bearing diorite, foid monzodiorite, and foid diorite. Diorite would have roughly equal amounts of these minerals. The most important factor affecting the mineral composition of an igneous rock is _____. 2. determine color/composition: mostly light minerals = felsic; half light, half black (or gray in fine grained rocks) = intermediate; mostly black minerals = mafic; mostly olivine = ultramafic Posted on August 31, 2014 by triplejunction. Mafic Rock. Ottawa: Geological Survey of Canada, CS1 maint: multiple names: authors list (, "Diorites and associated intrusive and metamorphic rocks of the Darran Complex, Mount Underwood, Milford, southwest New Zealand", https://en.wikipedia.org/w/index.php?title=Diorite&oldid=999759606, Short description is different from Wikidata, Creative Commons Attribution-ShareAlike License, This page was last edited on 11 January 2021, at 20:40. Compilations of many rock analyses show that rhyolite and granite are felsic, with an average silica content of about 72 percent; syenite, diorite, and monzonite are intermediate, with an average silica content of 59 percent; gabbro and basalt are mafic, with an average silica content of 48 percent; and peridotite is 15% 45% 85% 5% 30% 60% 95% Figure A5.5.1 The mafic minerals in photo A are shown as black areas in map B. Although diorite is rough-textured in nature, its ability to take a polish can be seen in the diorite steps of St. Paul's Cathedral, London, where centuries of foot traffic have polished the steps to a sheen. Granite would be a felsic rock type, and basalt would be a mafic rock type. intermediate mafic felsic granite, rhyolite) (diorite, andesite) (basalt, gabbro (peridotite, etc.) The color index of igneous rocks is a very useful indicator of the types of minerals present in the rock and therefore the specific type of rock. diorite. Also, is gabbro an Aphanitic? Composite Cone 11. Ødegården Verk, Norway. Diorite is an intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar (typically andesine), biotite, hornblende, and/or pyroxene. [3] Minor amounts of muscovite may also be present. This diorite is more salt than pepper, but it appears to have less than 10% quartz and no K-feldspar. Schist - Metamorphic. basalt gabbro diorite granite. Pyroclastic Flow 13. Gabbro is mafic and darker colored - may be greenish. … APHANITIC TEXTURE - Igneous rocks that form on the earth's surface havevery fine-grained texture because the crystals are too small to see withoutmagnification. extrusive, felsic porphyritic texture gray/greenish crystals (class sample is distinct red color) Porphyritic Andesite. Many samples of diorite display a 'salt-and-pepper' texture due to the near-equal mixture of light- and dark-colored minerals. 1. determine texture: coarse-grained (visible crystals) = plutonic, fine-grained (microscopic crystals), or porphyritic (visible crystals in fine groundmass) = volcanic. Geochemical composition indicates that Beehive Diorite is a calc‐alkaline cumulate derived from a primitive source in a volcanic arc setting, and provides a baseline for Darran Suite mafic magmatism at Lake Manapouri. Amphibolite is a metamorphic rock with roughly the same composition. Classification of Igneous Rocks. Senja, Norway. What is the approximate silica content of a granite? Diorite is an intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar, biotite, hornblende, and/or pyroxene. Use the scale above to estimate the percentage of mafic minerals in this rock. Other Characteristics: found as both lava and pyroclastic tuff. Similar rocks are gabbro (pyroxene-plagioclase rock, contains more mafic minerals and plagioclase is calcic), monzodiorite (contains more alkali feldspar) and quartz diorite (contains 5-20% quartz). K2O — 1.79 Diorite was used by both the Inca and Mayan civilizations, but mostly for fortress walls, weaponry, etc. The chemical composition of diorite is intermediate, between that of mafic gabbro and felsic granite. Granite, diorite and gabbro are phaneritic rocks because they solidify slowly during which time crystals grow large enough in size to be visible to the naked eye. Unfortunately, I have no super close-up for you. Its volcanic (fine-grained) analogue is andesite. Marble - Metamorphic. Width of sample 8 cm. schist - metamorphic rock that cannot fall into these categories . diorite: mafic: Ca-plagioclase, pyroxene, olivine, amphibole: gabbro: ... glass (may contain a few minerals typical of felsic rocks) pumice: mafic: glass (may contain a few mineral typical of mafic rocks) scoria: Note: Basalt with fewer holes, known as vesicles, is called vesicular basalt. Obsidian is a natural glass - it lacks crystals, and therefore lacks minerals. Question 1 1 pts Is diorite mafic, felsic, intermediate, or ultramafic in composition? Sample from Hannukainen, Finland. conglomerate - sedimentary rock that is more felsic than mafic Conglomerate - Clastic Sedimentary. It occurs in both continental and oceanic crust and is not a rare rock type, but it is significantly less common than granite and other granitoids. Mafic Rocks and Rhyolite We have granite, which is intrusive felsic, diorite, which is intrusive intermediate, and andesite, which is extrusive intermediate. Felsic is a generic term meaning enriched in feldspar and silica (and thus generally lower in iron and magnesium). Diorite (red) on the QAPF diagram. Porphyritic Rhyolite. Learn vocabulary, terms, and more with flashcards, games, and other study tools. ... diorite. Intrusive Igneous Rocks 2. Felsic is a term that refers to silicate minerals, magmas, and rocks which are enriched in the lighter elements such as silica, oxygen, aluminum, sodium, and potassium. 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